Process of photoengraving



May 18, 1937. H. FUNCK 2,080,965

. PROCESS 0F PHOTOENGRAVING o riginal Filed Feb. 25, 1932 v INVENTOR. I v flame) fZ/NcK.

ATTORNEY-5.

Patented May 18, 1937 UNITED STATES PATENT OFFICE A Application February 25, 1932, Serial No. 595,112

Renewed October 17, 1936 16 Claims.

This invention resides in a new and novel process of producing an engraved plate for printmg purposes.

The principal object of the invention is to produce such a plate through a photomechanical process which. will greatly decrease the labor usually required in the known and practiced methods, decrease the time required for producing engraved plates and further, simplify the process so that the cost is minimized, while at the same time producing a plate having greater wearing qualities so as to be capable of making many more impressions.

In accordance with this invention, a halftone negative, having all possible tone-value, such as an offset negative, will produce an engraved printing plate in a very few minutes by photomechanical means, whereas it would take some time for an artist to produce a similar plate by fine or re-etching in accordance with the present practice.

The principal feature of the invention resides in applying a photo-sensitive substance having certain characteristics required for the purpose, to a plate which may be of any hard and rigid substance such as bakelite, glass, wood, metal,

fiber or the like, no particularmetal or substance being required. Thus, the material from which the base or foundation of the plate is made is. in itself considerably cheaper than the metals usually required for etching.

The photo-sensitive composition may be applied according to the desired depth of the engraving. For instance, for fine printing work, the screen or lines may be finer and consequently the depth of the engraving less, whereas in rough work such as news print, the screen or lines are coarse and consequently the depth of the engraving has to be greater.

The process practiced in photoengraving is carried out to the extent of producing a screen or line negative. Thereafter, this. invention departs from the usual practice in that it is only necessary to apply the screen or line negative over the sensitizedsurface of the plate, expose the same to the light for a few minutes, and pass the plate through a developing bath and dry the same, whereupon it is ready for use. This distinguishes from the long, tedious and elaborate process usually required wherein the engraving plate has a light sensitive-coating applied thereto over which the screen negative is placed,

whereupon'it is exposed to the light for a substantial length of time and thereupon submerged in a developing bath after which.1t is treated with a protective substance to form an acid resist, which is a tedious and highly specialized art, and then submerged in the etching bath, these last two operations being repeated from one to three times, thus requiring a substantial lengtli of time in treatment, as well as requiring most expert labor.

In addition to the reduced time and labor saving process as above pointed out, certain other material advantages in the-fineness of the work and its durability result. Whereas in the practiced photoengraving process, the dots formedin the plate are to some extent undermined by the eating-in of the acid laterally, as well as downwardly, in applicants process the substance is effected only by the light penetration, so that the tendency is for the recesses to be straight. This leaves a' substantial base for the support of the dots formed in the surface as will be hereinafter more specifically pointed out. Consequently, the surface of the dots is more substantial in applicant's process than in the practiced photoengraving.

A further important advantage in respect to this feature resides in the fact that the under mining of the dotsin the practiced photo-engraving process tends to destroy the matrix, wax or lead molding wherein the impression thereof over the surface of the plate forces the material between the undermined dots where it spreads and tears out 'when removed. This difficulty is entirely eliminated in applicant's process since there is no undermining and the matrix or sheets may be readily removed without tear or mutilation.

A still further advantage resides in the fact that wherein the plate is used for direct printing, the surface of the sensitized and developed substance has a natural tendency to give oi! the ink to the paper more readily than the engraved 40 metal plates used in the present practice.

Furthermore, the surface characteristics of the substance used-on applicants plate is such as to give sufiicient elasticity to increase the wearing qualities as compared with the rigid inelastic surface of the copper and especially zinc surface of the photoengraved plate.

A further advantage of ,applicants process is the fact that the engraving plate which may be made of various materials as above mentioned may be readily glued or cemented to the block so that it is unnecessary to tack it in position as is the usual practice with copper or zinc plates. While it may be possible to secure the copper or zinc plates in the same manner, it is dimcult and impractical to do so. Furthermore, by thus securing the plate to the block, the formation of a bevel customarily employed for tacking is elim-'- inated.

One feature of applicants process resides in forming the photo-sensitive substance with varying degrees of sensitivity, wherein the sensitivity of the substance will increase from the exposed surface to the base. This is for the purpose of permitting the light rays which decrease in strength as they penetrate the depth of the substance, to equally affect the substance throughout its entire depth. By providing the substance with greater sensitivity as its depth increases, the decrease in the efficiency of the light rays will be compensated for or equalized. Thus, with a short exposure, a clean-cut dot or line formation is obtained, but more important, the supporting base of the dots is strengthened. Otherwise, the strengthening effect of the light rays would not sufliciently penetrate throughout the depth of the dot to harden and thereby strengthen the base of the dot. 1

Another feature of the invention resides in the development of the substance after exposure in suchmanner as to maintain its true configuration and'prevent swelling. The characteristics of the substance are such that the tendency in the development after exposure is to swell and in the subsequent drying disfigure the true formation of the dots, which objection is avoided, as will be hereinafter more fully set forth.

A further feature of the invention resides in the employment of an aniline dye in the makeup of the substance which will correct the photo-activity of the substance to prevent halation, or the spreading of the light beyond its proper boundary with the help of the usual darkened base surface, all of which will be hereinafter more specifically referred to in the following description.

Other features of the invention consist in the composition of the sensitized substance and the solution in which it is developed after exposure, as will be hereinafter pointed out, coupled with the method of applying or forming the substance on the supporting plate.

The full nature of the invention will be more clearly understood from the accompanying drawing and the following description and claims:

Fig. 1 is a perspectiveview of' the engraving ,plate and block showing the finished engraved surface thereon. Fig. 2 is an enlarged section illustrative of the dotsand cuts in the engraved substance. Fig. 3 is a diagrammatical illustration greatly exaggerated showing the screen negative mounted over the engraving substance.

In the drawing there is shown a substantialy enlarged and exaggerated view of a printer's block ID on which is secured an engraving plate II which may be cemented or otherwise secured upon the block without the usual provision of bevels or flanges to permit tacking. A photosensitive substance I! is applied over the surface of the plate II to the thickness desired for obtaining the proper depth of engraving, depending upon the screen to be used, i. e., a fine screen or a coarse screen. The engraving plate which is preferably made of bakelite or any other similar material having a smooth hard surface and which may include metal, wood or the like, is usually of sixteen gauge or .0625 inch on an average in thickness, whereas the photo-sensitive engraving substance I! for comme c a pu p ses to .008 inch in thickness.

The plate H with the engraving substance thereon, for commercial purposes, is manufactured in strips of convenient size and shipped to the engravers or users thereof in sealed containers so as not to be exposed to the light and may thereupon be cut to the desired dimensions for use as occasion warrants.

Wherein such plates are formed of metal, the,

surface thereof must be neutralized by a coating of lacquer or varnish to prevent oxidizing which, of course, is not required with non-metallic plates. Furthermore, wherein the plates are made out of metal, they cannot be readily secured by adhesion and it is, therefore, advisable to provide the usual bevel and tack them to the block. Consequently, a bakelite" or fiber plate pending upon the power of the light. It is then taken to the dark room, the screen negative removed and the sensitized surface and plate submerged into a developing bath as will be hereinafter more specifically described. It is submerged in the developing bath approximately one and one-half minutes and is then dried. Immediately upon being dried, it is ready for printing.

As will be noted in Fig. 3, the dots indicated by the numeral M are formed in the engraving substance by recesses I5 extending throughout the entire thickness of the substance. The dots and recesses are formed by the exposure of the sensitized substance to light through the screen negative. The effect of the light thereon is to harden the substance penetrated so as to make it impervious to the developing bath.

Thus, where there is an open or white space in the scren or line negative, there will be a dot or line I4 and where there is a closed or black space, there will be formed the recess l5. That portion of the surface of the substance which is exposed to the light becomes hardened equally throughout its entire thickness and will not be affected by the solution in which the substance is developed, whereas the solution dissolves the non-exposed portion of the substance, leaving the recesses l5. In this connection, it may be noted that the light hardens and renders impervious to the solution not only the surface of the substance which it strikes, but penetrates through the entire thickness of the substance so that no dissolving thereof will occur. For this reason, the light rays striking the substance in a substantially vertical direction to its surface, the dots will be formed with substantially vertical and parallel side surfaces, presenting a clean-cut dot formation and a firm and solid base for the support thereof as distinguished from the rougher clot formation and under-cutting of the acid in the practised photoengraving process. Inasmuch as the substance I! adheres firmly to the plate I I and becomes for all practical purposes an integral part thereof, the dots will stand up longer under the strain thereon from many impressions and the surface, being is made in three thicknesses, rangingfrom .0015 I stance has become hardened. -Thus, the several layers of substance are all applied in a liquid chemically hardended bythe light, will wear indefinitely. a

While it is possible that other substances may be employed for producing the sensitized engraving surface I2, the following formula is suggested as the most satisfactory now known.

With a body of chromated colloid prepared to the desired sensitivity, and preferably chromated gelatin, there is mixed a small amount of copper chloride, tartrazine dye and a lesser amount of glycerin. The chromated colloid provides the body of the sensitized substance, whereas, the tartrazine dye is employed for the purpose of preventing halation, while the purpose of the glycerin is to eliminate tension of the substance. To ap-.

proximately 1000 parts of the chromated colloid or gelatin, there is mixed approximately 5 parts of copper chloride, 2 parts of tartrazine dye and ready for use.

The substance in liquid form at about 50? C. to 60 C. can most conveniently be applied-by the usual spray gun, wherein it is sprayed over the surface of the base plate to the desired thickness.

As to thickness in commercial use, it is best practice to employ three commercial thicknesses as above set forth which may be gauged by theamount of substance sprayed over a given. area of the surface. It is important, however, that the light ray penetrates the entire thickness of the substance with substantially the same effect on its sensitivity. One method of building up the substance so as to increase its sensitivity from the exposed surface inwardly, is to provide two or more layers of substance having varying degrees of sensitivity. To accomplish this, the first or base coating of the material contains a'higher percentage of a chrome salt in the colloid, whereas the succeeding layers or applications of the substance have a lesser percentage of chrome. This may be accomplished by making up several solutions of the substance embodying varying percentages of chrome and using separate air guns for each solution, applying the more sensitive solution first with an air gun and thereafter immediately applying the subsequent layers of substance having less or lower sensitivity, before the preceding substate and, therefore, become fused into one integral composition which is less sensitive toward the exposed surface.

Upon the sensitized substance becoming substantially hardened, it is then ready for packaging and commercial use as above set forth. However, to prolong its life, for shipment, storage and commerical use, a small percentage of citric acid may be employed, the acid being mixed with the ingredients of the above substance in the amount of approximately 2 /2 parts of citric acid to 1000 parts of colloid.

After the substance is'exposed to the light, it is then developed ina subdued light, the'develop ing' solution containing ingredients such as alcohol, 'formalin or chrome alum, which prevent swelling of the colloid and provide a clean-cut engraved dot or line formation. A mostsatisfactory developerconsists of any kind of alcohol (denatured) diluted to about 40%, and used at a coatings.

temperature of between 35 C. and 45 C. In effecting the development, the exposed sensitized substance -on its supporting plate is immersed in the solution between one and two minutes, whereupon the unexposed surface and corresponding point to adopt the following practice. This may occur in shipping the plates to tropical countries or storing the plates over a substantial length of time. In such instances, the colloid may be used I without chrome salt, wherefore the substance would have no sensitivity and therefore, it would not be aflected by climatic or atmospheric conditions. When ready ,for use, sensitivity may be imparted'to the substance by immersing 'it in a 2 bichromate solution containing a small amount of alcohol at 18C. Such solution would impart the necessary sensitivity to the substance,

giving it the same reactive effect to light as above set forth.

In order that there may be a variation ing the sensitivity of the substance through its depth for the reasons and in the manner above mentioned, the substance or colloid when originally prepared and applied to the supporting plate, may contain varying amounts of a copper salt, the copper salt having the efiect of increasing the sensitivity when sensitized by the chrome salt solution. Therefore, in the varying depths of the colloid coating, variation in sensitivity is effected in accordance therewith.

- The invention claimed is: v 1. The process of making a light sensitive printing plate adapted to be processed for relief etching, consisting in applying a substantialing a chrome colloid for rendering the same 4 sensitive to light, and thereafter applying a second substantially liquid coating of chrome colloid over the first coating having a lesser amount of chrome salt therein to decrease the sensitivity of the superposed coating, said second coating being applied while the first coating is still in its fluid state to cause a fusing of the two 3. The process of making a light sensitive printing plate adapted to be processed for relief etching, consisting in applying a coating of light sensitive substance including a copper salt therein to a supporting surface, and thereupon applying a second coating having a lesser amount of copper salt, said second coating being appliedv over the first coating while in a plastic state.

4. The process of making a light sensitive plate adapted to be processed for relief etching, consisting in applying a coating of colloid including a copper salt therein to a supporting surface,

fusing therewith while-in a plastic state a sec- 0nd coating of colloid having a lesser amount of copper salt, and thereafter treating the same to a bichromate solution.

5. The process of making an engraved plate consisting in applying a coating of colloid over the surface of a supporting base, rendering said colloid coating sensitive 'to light, exposing the same to light through a negative and thereafter developing the coating in a solution of diluted alcohol, and thereafter further hardening the developed coating in an alcohol formaldehyde solution, for preventing the swelling of the colloid.

6. The process of making an engraved plate consisting in applying to a supporting surface a coating of light sensitive substance including a. body of chromated colloid with which is mixed a relatively small amount of copper chloride,

tartrazine dye and glycerin, exposing said substance to light through a negative and thereafter immersing the same in diluted alcohol as a developer.

7. The process of making an engraved plate consisting in applying to a supporting surface a coating of light sensitive substance including a body of. chromated colloid with which is mixed a relatively small amount of copper chloride, tartrazine dye and glycerin, exposing said substance to light through a negative and thereafter immersing the same in diluted alcohol as a developer, and finally immersing the developed plate in an alcoholic formaldehyde solution for hardening the surface thereof.

8. A light sensitive substance adapted to be applied to a supporting surface, including a body of chromated colloid, copper chloride, tartrazine dye and glycerin.

9. A light sensitive substance adapted to beapplied to a supporting surface, including one thousand parts of chromated colloid or gelatin, with which is incorporated approximately five parts of copper chloride,-approximately two and one-half parts of tartrazine dye and approximately one part of glycerin.

10. A light sensitive substance adapted to be applied to a supporting surface, including a plurality of coatings applied one upon the other while in a plastic state, each of said coatings including chromated colloid or gelatin in which is embodied a copper chloride, a tartrazin'e dye and glycerin, the inner coating having a greater amount of copper chloride and/or bichromate salt than the outer coating, whereby said inner coating will have greater sensitivity than the outer coating.

11. The process of producing an engraved plate consisting in mixing a solution of chromated colloid or gelatin of one thousand parts with approximately five parts of copper chloride,

. approximately two and one-half parts tartrazine dye and approximately one part of glycerin, heating the same to approximately C. and applying it upon the cleansed smooth surface of a supporting base, applying thereover a second coating having a lesser amount of copper chloride and/or bichromate salt to render the same less sensitive and while the first coating is still in a plastic state, cooling the same to 'a hardened state, exposing the substance to light through a negative, and thereafter immersing the same in a solution of about 40% alcohol at a temperature of about 40 C.

12. A process of making an engraved plate consisting in applying a coating of colloid over the surface of a supporting base, rendering said colloid coating sensitive to light, exposing the same to light through a negative, developing over the surface of a supporting base, said coating including copper salts, the lower portion of the coating including a greater concentration of copper salts than the upper portion of the coating, thereafter submerging the coating in a bichromate solution to render the same sensitive to light, the lower portions of the coating thus being rendered more sensitive to light than the upper portions of the coating.

14. A process of making a half-tone printing plate, including applying a coating of colloid over the surface of a supporting base, said coating including'copper salts, the lower portion of the coating including a greater concentration of copper salts than the upper portion of the coating, thereafter submerging the coating, in a bichromate solution to render the same sensitive to light, the lower portions of the coating thus being rendered more sensitive to light than the upper portions of the coating, exposing the same from the emulsion side to light through a screened negative, and then submerging the' same in a developing bath to remove the nonexposed portion of the colloid, thereby leaving half-tone dots of the exposed portion of the colloid suitable for half-tone printing.

15. A half-tone printing plate, comprising a rigid supporting base and half-tone dots of a developed light sensitive gelatin containing coiloid' on said base and possessing substantially perpendicular and clean-cut sides so that dots are directly usable in half-tone printing.

16. A half-tone printing plate, comprising a rigid supporting base and half-tone printing dots 

